Ejemplo n.º 1
0
        public static void PrimvarsTest()
        {
            var sample  = PrimvarSample.GetTestSample();
            var sample2 = new PrimvarSample();
            var scene   = USD.NET.Scene.Create();

            scene.Write("/Foo", sample);

            PrintScene(scene);

            var prim = scene.Stage.GetPrimAtPath(new pxr.SdfPath("/Foo"));

            var garply = prim.GetAttribute(new pxr.TfToken("nested:foo:bar:garply"));

            AssertTrue(garply.GetNamespace() == new pxr.TfToken("nested:foo:bar"));

            var primvar = new pxr.UsdGeomPrimvar(
                prim.GetAttribute(new pxr.TfToken("primvars:somePrimvar")));

            AssertEqual(primvar.GetElementSize(), 1);

            primvar = new pxr.UsdGeomPrimvar(
                prim.GetAttribute(new pxr.TfToken("primvars:somePrimvar1")));
            AssertEqual(primvar.GetElementSize(), 1);

            primvar = new pxr.UsdGeomPrimvar(
                prim.GetAttribute(new pxr.TfToken("primvars:somePrimvar2")));
            AssertEqual(primvar.GetElementSize(), 2);

            primvar = new pxr.UsdGeomPrimvar(
                prim.GetAttribute(new pxr.TfToken("primvars:skel:jointIndices")));
            AssertEqual(primvar.GetElementSize(), 3);

            primvar = new pxr.UsdGeomPrimvar(
                prim.GetAttribute(new pxr.TfToken("primvars:nested:foo:bar:baz")));
            AssertEqual(primvar.GetElementSize(), 4);

            sample2.nestedSample = new PrimvarSample.NestedSample();
            scene.Read("/Foo", sample2);

            AssertEqual(sample.somePrimvar, sample2.somePrimvar);
            AssertEqual(sample.somePrimvar1, sample2.somePrimvar1);
            AssertEqual(sample.somePrimvar2, sample2.somePrimvar2);
            AssertEqual(sample.jointIndices, sample2.jointIndices);
            AssertEqual(sample.nestedSample.baz, sample2.nestedSample.baz);
            AssertEqual(sample.nestedSample.garply, sample2.nestedSample.garply);

            //
            // Test deserialization without nested object instantiated.
            //
            sample2 = new PrimvarSample();
            sample2.nestedSample = null;
            scene.Read("/Foo", sample2);

            AssertEqual(sample.somePrimvar, sample2.somePrimvar);
            AssertEqual(sample.somePrimvar1, sample2.somePrimvar1);
            AssertEqual(sample.somePrimvar2, sample2.somePrimvar2);
            AssertEqual(sample.jointIndices, sample2.jointIndices);
            AssertEqual(null, sample2.nestedSample);
        }
        static void ExportMesh(ObjectContext objContext,
                               ExportContext exportContext,
                               Mesh mesh,
                               Material sharedMaterial,
                               Material[] sharedMaterials,
                               bool exportMeshPose = true)
        {
            string path = objContext.path;

            if (mesh == null)
            {
                Debug.LogWarning("Null mesh for: " + path, objContext.gameObject);
                return;
            }

#if UNITY_EDITOR
            if (!CanReadMesh(mesh))
            {
#else
            if (!mesh.isReadable)
            {
#endif
                Debug.LogError(
                    "Mesh is not readable: " + objContext.path +
                    ". To fix this, enable read/write in the inspector for the source asset that you are attempting to export.",
                    objContext.gameObject);
                return;
            }

            var scene                  = exportContext.scene;
            bool unvarying             = scene.Time == null;
            bool slowAndSafeConversion = exportContext.basisTransform == BasisTransformation.SlowAndSafe;
            var sample                 = (MeshSample)objContext.sample;
            var go = objContext.gameObject;

            if (mesh.bounds.center == Vector3.zero && mesh.bounds.extents == Vector3.zero)
            {
                mesh.RecalculateBounds();
            }

            sample.extent = mesh.bounds;

            if (slowAndSafeConversion)
            {
                // Unity uses a forward vector that matches DirectX, but USD matches OpenGL, so a change of
                // basis is required. There are shortcuts, but this is fully general.
                sample.ConvertTransform();
                sample.extent.center = UnityTypeConverter.ChangeBasis(sample.extent.center);
            }

            // Only export the mesh topology on the first frame.
            if (unvarying)
            {
                // TODO: Technically a mesh could be the root transform, which is not handled correctly here.
                // It should have the same logic for root prims as in ExportXform.
                sample.transform = XformExporter.GetLocalTransformMatrix(
                    go.transform,
                    scene.UpAxis == Scene.UpAxes.Z,
                    new pxr.SdfPath(path).IsRootPrimPath(),
                    exportContext.basisTransform);

                sample.normals  = mesh.normals;
                sample.points   = mesh.vertices;
                sample.tangents = mesh.tangents;

                sample.colors = mesh.colors;
                if (sample.colors != null && sample.colors.Length == 0)
                {
                    sample.colors = null;
                }

                if ((sample.colors == null || sample.colors.Length == 0) &&
                    (sharedMaterial != null && sharedMaterial.HasProperty("_Color")))
                {
                    sample.colors    = new Color[1];
                    sample.colors[0] = sharedMaterial.color.linear;
                }

                // Gah. There is no way to inspect a meshes UVs.
                sample.st = mesh.uv;

                // Set face vertex counts and indices.
                var tris = mesh.triangles;

                if (slowAndSafeConversion)
                {
                    // Unity uses a forward vector that matches DirectX, but USD matches OpenGL, so a change
                    // of basis is required. There are shortcuts, but this is fully general.

                    for (int i = 0; i < sample.points.Length; i++)
                    {
                        sample.points[i] = UnityTypeConverter.ChangeBasis(sample.points[i]);
                        if (sample.normals != null && sample.normals.Length == sample.points.Length)
                        {
                            sample.normals[i] = UnityTypeConverter.ChangeBasis(sample.normals[i]);
                        }

                        if (sample.tangents != null && sample.tangents.Length == sample.points.Length)
                        {
                            var w = sample.tangents[i].w;
                            var t = UnityTypeConverter.ChangeBasis(sample.tangents[i]);
                            sample.tangents[i] = new Vector4(t.x, t.y, t.z, w);
                        }
                    }

                    for (int i = 0; i < tris.Length; i += 3)
                    {
                        var t = tris[i];
                        tris[i]     = tris[i + 1];
                        tris[i + 1] = t;
                    }
                }

                sample.SetTriangles(tris);

                UnityEngine.Profiling.Profiler.BeginSample("USD: Mesh Write");
                scene.Write(path, sample);
                UnityEngine.Profiling.Profiler.EndSample();

                // TODO: this is a bit of a half-measure, we need real support for primvar interpolation.
                // Set interpolation based on color count.
                if (sample.colors != null && sample.colors.Length == 1)
                {
                    pxr.UsdPrim usdPrim      = scene.GetPrimAtPath(path);
                    var         colorPrimvar =
                        new pxr.UsdGeomPrimvar(usdPrim.GetAttribute(pxr.UsdGeomTokens.primvarsDisplayColor));
                    colorPrimvar.SetInterpolation(pxr.UsdGeomTokens.constant);
                    var opacityPrimvar =
                        new pxr.UsdGeomPrimvar(usdPrim.GetAttribute(pxr.UsdGeomTokens.primvarsDisplayOpacity));
                    opacityPrimvar.SetInterpolation(pxr.UsdGeomTokens.constant);
                }

                string usdMaterialPath;
                if (exportContext.exportMaterials && sharedMaterial != null)
                {
                    if (!exportContext.matMap.TryGetValue(sharedMaterial, out usdMaterialPath))
                    {
                        Debug.LogError("Invalid material bound for: " + path);
                    }
                    else
                    {
                        MaterialSample.Bind(scene, path, usdMaterialPath);
                    }
                }

                // In USD subMeshes are represented as UsdGeomSubsets.
                // When there are multiple subMeshes, convert them into UsdGeomSubsets.
                if (mesh.subMeshCount > 1)
                {
                    // Build a table of face indices, used to convert the subMesh triangles to face indices.
                    var faceTable = new Dictionary <Vector3, int>();
                    for (int i = 0; i < tris.Length; i += 3)
                    {
                        if (!slowAndSafeConversion)
                        {
                            faceTable.Add(new Vector3(tris[i], tris[i + 1], tris[i + 2]), i / 3);
                        }
                        else
                        {
                            // Under slow and safe export, index 0 and 1 are swapped.
                            // This swap will not be present in the subMesh indices, so must be undone here.
                            faceTable.Add(new Vector3(tris[i + 1], tris[i], tris[i + 2]), i / 3);
                        }
                    }

                    var usdPrim     = scene.GetPrimAtPath(path);
                    var usdGeomMesh = new pxr.UsdGeomMesh(usdPrim);

                    // Process each subMesh and create a UsdGeomSubset of faces this subMesh targets.
                    for (int si = 0; si < mesh.subMeshCount; si++)
                    {
                        int[] indices     = mesh.GetTriangles(si);
                        int[] faceIndices = new int[indices.Length / 3];

                        for (int i = 0; i < indices.Length; i += 3)
                        {
                            faceIndices[i / 3] = faceTable[new Vector3(indices[i], indices[i + 1], indices[i + 2])];
                        }

                        var vtIndices = UnityTypeConverter.ToVtArray(faceIndices);
                        var subset    = pxr.UsdGeomSubset.CreateUniqueGeomSubset(
                            usdGeomMesh,            // The object of which this subset belongs.
                            m_subMeshesToken,       // An arbitrary name for the subset.
                            pxr.UsdGeomTokens.face, // Indicator that these represent face indices
                            vtIndices,              // The actual face indices.
                            m_materialBindToken     // familyName = "materialBind"
                            );

                        if (exportContext.exportMaterials)
                        {
                            if (si >= sharedMaterials.Length || !sharedMaterials[si] ||
                                !exportContext.matMap.TryGetValue(sharedMaterials[si], out usdMaterialPath))
                            {
                                Debug.LogWarning("Invalid material bound for: " + path + "\n"
                                                 + (si >= sharedMaterials.Length
                                        ? "More submeshes than materials assigned."
                                        : (!sharedMaterials[si]
                                            ? "Submesh " + si + " has null material"
                                            : "ExportMap can't map material")));
                            }
                            else
                            {
                                MaterialSample.Bind(scene, subset.GetPath(), usdMaterialPath);
                            }
                        }
                    }
                }
            }
            else
            {
                // Only write the transform when animating.
                var meshSample = new MeshSampleBase();
                meshSample.extent    = sample.extent;
                meshSample.transform = XformExporter.GetLocalTransformMatrix(
                    go.transform,
                    scene.UpAxis == Scene.UpAxes.Z,
                    new pxr.SdfPath(path).IsRootPrimPath(),
                    exportContext.basisTransform);

                if (exportMeshPose)
                {
                    meshSample.points = mesh.vertices;

                    // Set face vertex counts and indices.
                    var tris = mesh.triangles;

                    if (slowAndSafeConversion)
                    {
                        // Unity uses a forward vector that matches DirectX, but USD matches OpenGL, so a change
                        // of basis is required. There are shortcuts, but this is fully general.
                        for (int i = 0; i < meshSample.points.Length; i++)
                        {
                            meshSample.points[i] = UnityTypeConverter.ChangeBasis(meshSample.points[i]);
                        }

                        for (int i = 0; i < tris.Length; i += 3)
                        {
                            var t = tris[i];
                            tris[i]     = tris[i + 1];
                            tris[i + 1] = t;
                        }
                    }

                    sample.SetTriangles(tris);
                }

                UnityEngine.Profiling.Profiler.BeginSample("USD: Mesh Write");
                scene.Write(path, meshSample);
                UnityEngine.Profiling.Profiler.EndSample();
            }
        }
    }
Ejemplo n.º 3
0
        /// <summary>
        /// Internal helper for reading data from USD.
        /// </summary>
        /// <param name="attrName">The USD attribute name.</param>
        /// <param name="csType">The C# type.</param>
        /// <param name="csValue">The C# value to populate.</param>
        /// <param name="usdTime">The time at which to sample key frames.</param>
        /// <param name="prim">The USD prim from which to read data.</param>
        /// <param name="memberInfo">The field/property providing serialization metadata.</param>
        /// <param name="usdNamespace">The optional USD namespace at which values live.</param>
        /// <param name="accessMap">A map of members to include when reading.</param>
        /// <param name="mayVary">When not null, is populated with variability.</param>
        /// <returns>True on success.</returns>
        /// <remarks>
        /// Note that "success" in the return value does not indicate data was read, rather it
        /// indicates that no unexpected states were encountered. E.g. calling ReadAttr on a field
        /// with no value stored in USD will not return false, since that is not considered a failure
        /// state.
        /// </remarks>
        bool ReadAttr(string attrName, Type csType, ref object csValue, pxr.UsdTimeCode usdTime,
                      pxr.UsdPrim prim, MemberInfo memberInfo,
                      HashSet <MemberInfo> accessMap, ref bool?mayVary,
                      string usdNamespace)
        {
            bool isNewPrimvar = csValue != null &&
                                csType.IsGenericType &&
                                csType.GetGenericTypeDefinition() == typeof(Primvar <>);
            bool   isPrimvar = Reflect.IsPrimvar(memberInfo) || isNewPrimvar;
            string ns        = IntrinsicTypeConverter.JoinNamespace(usdNamespace,
                                                                    Reflect.GetNamespace(memberInfo));


            // ----------------------------------------- //
            // Dictionaries, read, early exit, recurse.
            // ----------------------------------------- //
            // If holding a dictionary, immediately recurse and write keys as attributes.
            if (csValue != null &&
                csType.IsGenericType &&
                csType.GetGenericTypeDefinition() == typeof(Dictionary <,>) &&
                csType.GetGenericArguments()[0] == typeof(string))
            {
                Type genericTypeDef = csType.GetGenericArguments()[1].IsGenericType
                            ? csType.GetGenericArguments()[1].GetGenericTypeDefinition()
                            : null;

                isNewPrimvar = genericTypeDef == typeof(Primvar <>);
                bool isRelationship = csType.GetGenericArguments()[1] == typeof(Relationship);
                bool isConnection   = genericTypeDef == typeof(Connectable <>);

                // String dictionaries are unrolled directly into the object.
                // So the namespace is either the incoming namespace or empty, meaning each string value in
                // the dictionary becomes an attribute on the prim.

                // Ensure there is always a namespace immediately around this member.
                if (string.IsNullOrEmpty(Reflect.GetNamespace(memberInfo)))
                {
                    ns           = IntrinsicTypeConverter.JoinNamespace(ns, attrName);
                    usdNamespace = IntrinsicTypeConverter.JoinNamespace(usdNamespace, attrName);
                }

                // Unfortunately, the primvars prefixing logic must be replicated here so we can discover
                // the dictionary member from USD.
                if (isPrimvar || isNewPrimvar)
                {
                    ns = IntrinsicTypeConverter.JoinNamespace("primvars", ns);
                }

                var             dict = csValue as System.Collections.IDictionary;
                ConstructorInfo ctor = (isNewPrimvar || isConnection || isRelationship)
                             ? csType.GetGenericArguments()[1].GetConstructor(new Type[0])
                             : null;
                dict.Clear();
                foreach (var prop in prim.GetAuthoredPropertiesInNamespace(ns))
                {
                    object value = null;
                    if (ctor != null)
                    {
                        value = ctor.Invoke(new object[0]);
                    }
                    // The recursive call will also discover that this is a primvar and any associated namespace.
                    if (ReadAttr(prop.GetBaseName(),
                                 csType.GetGenericArguments()[1],
                                 ref value,
                                 usdTime,
                                 prim,
                                 memberInfo,
                                 accessMap,
                                 ref mayVary,
                                 usdNamespace))
                    {
                        if (value != null)
                        {
                            dict.Add(prop.GetBaseName().ToString(), value);
                        }
                    }
                }
                return(true);
            }

            pxr.TfToken sdfAttrName = sm_tokenCache[ns, attrName];

            // ----------------------------------------- //
            // Relationship, read + early exit.
            // ----------------------------------------- //

            if (csType == typeof(Relationship))
            {
                // mayVary is explicitly not set here because it has accumulation semantics:
                //   mayVary = mayVary || false;
                // Which is equivalent to the no-op:
                //   mayVary = mayVary;

                pxr.UsdRelationship rel = null;
                lock (m_stageLock) {
                    rel = prim.GetRelationship(sm_tokenCache[sdfAttrName]);
                }

                var relationship = new Relationship();
                csValue = relationship;

                if (rel == null || !rel.IsValid())
                {
                    return(true);
                }

                pxr.SdfPathVector paths  = rel.GetTargets();
                string[]          result = new string[paths.Count];
                for (int i = 0; i < paths.Count; i++)
                {
                    result[i] = paths[i].ToString();
                }

                relationship.targetPaths = result;
                return(true);
            }

            // ----------------------------------------- //
            // Connection Setup.
            // ----------------------------------------- //

            Connectable conn = null;

            if (csValue != null &&
                csType.IsGenericType &&
                csType.GetGenericTypeDefinition() == typeof(Connectable <>))
            {
                conn = csValue as Connectable;
                if (conn != null)
                {
                    // Since this is a Connectable<T>, the held value T is what's being read from USD,
                    // so replace csValue with the held T value itself. csValue must be restored before
                    // returning.
                    csValue = conn.GetValue();

                    // Same treatment for the type.
                    csType = conn.GetValueType();
                }
            }

            // ----------------------------------------- //
            // Primvar Setup.
            // ----------------------------------------- //

            ValueAccessor pvAccessor = null;
            PrimvarBase   pvBase     = null;

            if (isNewPrimvar)
            {
                pvAccessor = csValue as ValueAccessor;
                pvBase     = (PrimvarBase)csValue;
                // Since this is a Primvar<T>, the held value T is what's being read from USD,
                // so replace csVAlue with the held T value itself. csValue must be restored before
                // returning.
                csValue = pvAccessor.GetValue();

                // Same treatment for the type.
                csType = pvAccessor.GetValueType();
            }

            // ----------------------------------------- //
            // Lookup Type Conversion Delegate.
            // ----------------------------------------- //
            UsdTypeBinding binding;

            if (!sm_bindings.GetBinding(csType, out binding) &&
                !csType.IsEnum &&
                csType != typeof(object))
            {
                if (string.IsNullOrEmpty(ns))
                {
                    return(false);
                }

                var sample = csValue as SampleBase;
                if (csValue == null)
                {
                    // This could attempt to automatically constuct the needed object, then nullable objects
                    // could be used instead to drive deserialization.
                    return(false);
                }
                else if (sample == null)
                {
                    // In this case, csValue is not null, but also cannot be converted to SampleBase.
                    throw new ArgumentException("Type does not inherit from SampleBase: " + attrName);
                }

                Deserialize((SampleBase)csValue, prim, usdTime, accessMap, ref mayVary, usdNamespace: ns);
                return(true);
            }

            // ----------------------------------------- //
            // Prep to Read.
            // ----------------------------------------- //

            // Restore C# value to the actual property value.
            if (conn != null)
            {
                csValue = conn;
            }
            else if (pvAccessor != null)
            {
                csValue = pvAccessor;
            }

            // Append "primvars:" namespace to primvars.
            if (isPrimvar)
            {
                var joinedName = IntrinsicTypeConverter.JoinNamespace(ns, attrName);
                sdfAttrName = sm_tokenCache["primvars", joinedName];
            }

            // Adjust time for variability.
            pxr.SdfVariability variability = Reflect.GetVariability(memberInfo);
            pxr.UsdTimeCode    time        = variability == pxr.SdfVariability.SdfVariabilityUniform
                                          ? kDefaultUsdTime
                                          : usdTime;

            // Allocate a temp VtValue.
            pxr.VtValue vtValue = (pxr.VtValue)ArrayAllocator.MallocHandle(typeof(pxr.VtValue));

            try {
                // ----------------------------------------- //
                // Read Connected Paths.
                // ----------------------------------------- //
                if (conn != null)
                {
                    // Connection paths cannot be animated, so mayVary is not affected.
                    var sources = new pxr.SdfPathVector();
                    if (prim.GetAttribute(sdfAttrName).GetConnections(sources))
                    {
                        if (sources.Count > 0)
                        {
                            conn.SetConnectedPath(sources[0].ToString());
                        }
                    }
                }

                // ----------------------------------------- //
                // Read Associated Primvar Data.
                // ----------------------------------------- //
                // If this is a Primvar<T>, read the associated primvar metadata and indices.
                if (pvBase != null)
                {
                    var attr = prim.GetAttribute(sdfAttrName);
                    if (attr)
                    {
                        var pv = new pxr.UsdGeomPrimvar(attr);
                        // ElementSize and Interpolation are not animatable, so they do not affect mayVary.
                        pvBase.elementSize = pv.GetElementSize();
                        pvBase.SetInterpolationToken(pv.GetInterpolation());

                        // Indices are a first class attribute and may vary over time.
                        var indices = pv.GetIndicesAttr();
                        if (indices)
                        {
                            if (accessMap != null)
                            {
                                if (indices.GetVariability() == pxr.SdfVariability.SdfVariabilityVarying ||
                                    indices.ValueMightBeTimeVarying())
                                {
                                    accessMap.Add(memberInfo);
                                    mayVary |= true;
                                }
                            }
                            indices.Get(vtValue, time);
                            if (!vtValue.IsEmpty())
                            {
                                var vtIntArray = pxr.UsdCs.VtValueToVtIntArray(vtValue);
                                pvBase.indices = IntrinsicTypeConverter.FromVtArray(vtIntArray);
                            }
                        }
                    }
                }

                // ----------------------------------------- //
                // Read the value of csValue.
                // ----------------------------------------- //

                if (Reflect.IsMetadata(memberInfo))
                {
                    vtValue = prim.GetMetadata(sdfAttrName);
                    // Metadata cannot vary over time.
                }
                else if (Reflect.IsCustomData(memberInfo))
                {
                    vtValue = prim.GetCustomDataByKey(sdfAttrName);
                    // Custom data is metadata, which cannot vary over time.
                }
                else if (Reflect.IsFusedDisplayColor(memberInfo))
                {
                    vtValue = pxr.UsdCs.GetFusedDisplayColor(prim, time);

                    if (accessMap != null)
                    {
                        // Display color is actually two attributes, primvars:displayColor and
                        // primvars:displayOpacity.
                        var gprim = new pxr.UsdGeomGprim(prim);
                        if (gprim && gprim.GetDisplayColorAttr().ValueMightBeTimeVarying())
                        {
                            accessMap.Add(memberInfo);
                            mayVary |= true;
                        }
                    }
                }
                else if (Reflect.IsFusedTransform(memberInfo))
                {
                    vtValue = pxr.UsdCs.GetFusedTransform(prim, time);

                    if (accessMap != null)
                    {
                        // Transforms are complicated :/
                        var xformable = new pxr.UsdGeomXformable(prim);
                        if (xformable)
                        {
                            bool dummy;
                            var  orderAttr = xformable.GetXformOpOrderAttr();
                            if (orderAttr)
                            {
                                if (orderAttr.GetVariability() == pxr.SdfVariability.SdfVariabilityVarying &&
                                    orderAttr.ValueMightBeTimeVarying())
                                {
                                    mayVary |= true;
                                    accessMap.Add(memberInfo);
                                }
                                else
                                {
                                    foreach (var op in xformable.GetOrderedXformOps(out dummy))
                                    {
                                        var opAttr = op.GetAttr();
                                        if (!opAttr)
                                        {
                                            continue;
                                        }
                                        if (opAttr.GetVariability() == pxr.SdfVariability.SdfVariabilityVarying &&
                                            opAttr.ValueMightBeTimeVarying())
                                        {
                                            mayVary |= true;
                                            accessMap.Add(memberInfo);
                                            break;
                                        }
                                    } // foreach
                                }
                            }         // orderAttr
                        }             // xformable
                    }                 // mayVary
                }
                else
                {
                    if (accessMap != null)
                    {
                        var attr = prim.GetAttribute(sdfAttrName);
                        if (attr.GetVariability() == pxr.SdfVariability.SdfVariabilityVarying &&
                            attr.ValueMightBeTimeVarying())
                        {
                            accessMap.Add(memberInfo);
                            mayVary |= true;
                        }
                    }
                    if (!prim.GetAttributeValue(sdfAttrName, vtValue, time))
                    {
                        // Object has no value, still considered success.
                        return(true);
                    }
                }

                if (vtValue.IsEmpty())
                {
                    // Object has no value, still considered success.
                    return(true);
                }

                // ------------------------------------------ //
                // Infer C# type from USD when Type == Object
                // ------------------------------------------ //
                if (csType == typeof(object))
                {
                    // Blind object serialization needs special handling, since we won't know the C# type a priori.
                    // Instead, do a reverse lookup on the SdfTypeName and let USD dictate the C# type.
                    pxr.UsdAttribute attr = prim.GetAttribute(sdfAttrName);
                    if (attr != null && attr.IsValid())
                    {
                        // TODO: Assuming the reverse lookup is successful for the binding, the caller may be
                        // surprised by the result, since the USD <-> C# types are not 1-to-1. For example,
                        // a List<Vector2> may have been serialized, but Vector2[] may be read.
                        if (!sm_bindings.GetReverseBinding(attr.GetTypeName(), out binding))
                        {
                            if (string.IsNullOrEmpty(ns))
                            {
                                return(false);
                            }

                            // TODO: readback nested object declared as object -- maybe just disable this?
                            //Deserialize(ref csValue, prim, usdTime, usdNamespace: ns);
                            //return true;
                            return(false);
                        }
                    }
                    else
                    {
                        // TODO: Allow reading metadata declared as object in C#
                        return(false);
                    }
                }

                // ------------------------------------------ //
                // Convert USD's VtValue -> Strong C# Type.
                // ------------------------------------------ //
                csValue = binding.toCsObject(vtValue);

                // ------------------------------------------ //
                // Restore csValue.
                // ------------------------------------------ //
                if (conn != null && csValue != null)
                {
                    conn.SetValue(csValue);
                    csValue = conn;
                }
                if (pvAccessor != null)
                {
                    pvAccessor.SetValue(csValue);
                    csValue = pvAccessor;
                }
            } finally {
                // Would prefer RAII handle, but introduces garbage.
                ArrayAllocator.FreeHandle(vtValue);
            }

            return(true);
        }